Has anyone seen that problem and found a solution?
I am using WS2812B LED soldered on pucks, which are wired with red/green/white wires, and it seems these wires bounce the LED light and cast their green and red. 
The LED pucks are encased in hot glue and transparent shrink wrap to handle abuse.
I need to cast a white to warm white color (lowering blue LED),
so I wonder if there's a filter I could use or some trick...
if you have any ideas that work it'd be helpful.
Thanks.
I think you need a diffusers to mix the light. It sounds like you have point sources of the individual LEDs.
Yeah, the shroud is a diffuser, but the LEDs visibly cast what looks like marbled green and reddish/purple patterns.
I'm looking at putting a yellow or a white plastic wrap on top of the LEDs. That seems to help even if it's not great.
sonyhome:
the LEDs visibly cast what looks like marbled green and reddish/purple patterns.
Are you using RGB WS2812B or white WS2812B? You can get white from RGB but the individual colors will tend to show also if not thoroughly diffused so, as Grumpy_Mike indicated, this could be your problem rather than the wire colors. If you only need white then they have warm white WS2812B. If the issue actually is the wire colors then use white wire, just make sure to keep track of which is which.
pert:
If the issue actually is the wire colors then use white wire, just make sure to keep track of which is which.
Given the reference to "WS2812B LED soldered on pucks" I was about to suggest he was referring to these below, but research on eBay suggests that these modules are not available using WS2812s, but only WS2801/ 2811 which have a 4 wire connection.
Unless perhaps he meant these:
WS2811 is the same protocol as WS2812, just with external LEDs.
The 2801 is the one that has a clock line.
If the wires themselves are casting the shadow - why did you put the wires between the LED and the viewer?
And yeah, you need a diffuser of some sort to deal with the color shadow effect.
DrAzzy:
WS2811 is the same protocol as WS2812, just with external LEDs.
Either way, they do not seem to make them in the silicone-encapsulated "pucks" where the wiring itself may be actually relevant.
The OP does not seem to be particularly forthcoming with details as to the actual physical arrangement.